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Turbo Powered Snow Blower
 
Join Date: Mar 2016
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In addition to what Steve recommends checking ^^^
Does the 83 have the early piston and spring by-pass system? Maybe there is an issue with the seals in that? I've read the seals and connections leak there. Or possible a cracked hose to the decel valve? Something is leaking and can only hold .4bar before it blows. You will need to go through everything on the boost side as well as checking the waste gate.
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Derrick
Old 05-21-2018, 05:56 AM
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Derrick, not sure how it relates to the earlier models as there no doubt some changes or mods, but it does have a large spring loaded valve inside the throttle body just under the intercooler which appears to be operated by an external diaphragm (blowoff valve?). Will pull the IC again and focus more on this. I appreciate the help from all of you guys!

DK
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Deke
83 911SC
83 930
87 Targa
86 944
Old 05-21-2018, 10:41 AM
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Found an online manual, albeit for earlier models, the diaphragm I referred to is the idle air control valve. Although my throttle body is much larger and part of the intake manifold, it does have an internal spring/piston valve with seals at each end similar to the early models. Keep y'all posted.

DK
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83 911SC
83 930
87 Targa
86 944
Old 05-21-2018, 11:10 AM
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The 83 930 has the same intake manifold, by pass valve/BOV housing that looks like a cast manifold, and throttle body as the newer ones, albeit possibly with some slightly different vacuum nipples depending US, RoW etc. Pretty sure of that.

If the shuttle valve inside the BoV housing has bad seals you'll hear a loud "clack" noise when it moves back and forth in the housing. Its a super easy, cheap, and quick repair and with a car that vintage I'd go ahead and do it, but I don't think its your issue. If its the first time you've been into the car it will take you an afternoon. No special tools needed.

Get a manual, paper or electronic.
Old 05-21-2018, 11:30 AM
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Back from Le Mans, and have pulled the intercooler and charge pipe, seals all look OK, will pull the re-circ. bypass housing this weekend and check hoses & seals, keep y'all updated.


Deke
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83 911SC
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Old 06-27-2018, 06:33 PM
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I find it unusual that I lose all boost, and upon throttle lift regain it only to 0.4 bar. Correct me if I am wrong, but if it were a vacuum leak it would be consistent to pressure threshold level and I would have some boost, but only to 0.4 instead of dropping to zero each time.

This seems to be a very consistent valve issue, 0.4 bar is the limit and then no boost at all regardless of RPM, and then upon full throttle lift it appears to reset...but again only to 0.4 limit. Almost seems electronic, except there is not really any electronic controls on the system.
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Old 06-27-2018, 07:24 PM
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Mighty Meatlocker Turbo
 
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^^^

If you have a misfire during boost (for example, from an overly rich condition during full throttle/boost enrichment) you will have "no boost" at whatever the RPM the misfire occurs (no load on engine at that point and thus no boost), and then will regain boost once RPM drops below the misfire range.

Vacuum leaks tend to create overly rich conditions during boost with K-Jetronic/CIS as the system thinks more fuel is required than actually is.
Old 06-27-2018, 08:50 PM
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No misfire either, just loss of boost at 0.4, lift and reset...just bizarre!
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83 911SC
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Old 06-27-2018, 09:45 PM
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Raw, also see you are in Nth Tx, heard they are/were resurfacing ECR, always like that track, any update on that?
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83 911SC
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Old 06-27-2018, 09:50 PM
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Raw, after re-rereading your post and re-thinking it, that does make sense with regard to the symptoms, have not noticed any significant misfire, but only thing that makes sense is a vacuum leak somewhere...will chase it down and let all know. As always, thanks for your help Gents!
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Old 06-27-2018, 09:59 PM
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A loose intake mounting somewhere - like IC lifting off a mount point at 0.4 bar.? Or as mentioned, split/pinched O ring. I did have a loose mounting once and had a pulsing boost gauge. Not too hard to see how the symptoms could alter to what you have. Basically the boost is escaping somewhere at 0.4 bar. Split hose?
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 06-28-2018, 09:16 PM
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One possibility would be to try and pressurise the system to 0.4 bar. I pressurise mine to 5psi when looking for leaks. I don't go beyond this because the intake elbow hose is not made for pressure. But it does seem to survive at 5psi (near enough to 0.4 bar).
Alan
PS will post pic when I can find it.
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 06-28-2018, 09:36 PM
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 06-28-2018, 09:40 PM
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Update

IC seals and pressure pipe seals look ok, but will replace, tested WG and it opening as it should at 1.0 bar with new spring & diaphragm and no obvious leaks. Now onto re-circ. valve and throttle body seals & hoses.


Deke
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Old 06-29-2018, 01:27 PM
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Ideal time to upgrade to a long neck I/C ;-)
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81 Pacific Blue 930 Euro coupe slicktop on a strict diet, Rarlyl8 headers, Blowzilla turbo, Tial waste gate, Full bay I/C, Home made center out exhaust, Leask WUR, MSD 6AL, PLX wideband
Wevo shifter, LSD. Next up, Cams, Heads and port work
Old 06-29-2018, 07:27 PM
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930 boost issue

Found a loose clamp/connection to the turbo inlet, could this cause the re-circ. bypass valve to open prematurely? If so, this would explain loss off all boost and then reset upon throttle lift as the valve resets. Anyone ever experienced this?

Deke
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Old 06-30-2018, 11:13 AM
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Quote:
Originally Posted by knight44 View Post
Found a loose clamp/connection to the turbo inlet, could this cause the re-circ. bypass valve to open prematurely? If so, this would explain loss off all boost and then reset upon throttle lift as the valve resets. Anyone ever experienced this?

Deke
I didn't experience exactly the symptoms you did, but had similarly weird symptoms with loss of boost, weird backfiring, difficulty pinning it down after washing the engine with mineral spirits shortly after pulling in from storage. Was due to softening of the turbo neck to charge pipe seal.
Old 06-30-2018, 04:06 PM
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